1. Field of the Invention
The present invention relates to a liquid droplet ejecting apparatus and a liquid droplet ejecting method.
2. Background Technology
In the liquid droplet ejecting head for ejecting liquid droplets from nozzles such as an inkjet recording head (hereinafter referred to as “recording head” in some cases) for recording an image using minute ink particles, pressure is given into the pressure generation chamber so that ink particles are ejected from the nozzle, whereby ink particles are applied onto a recording medium such as recording paper.
There are a great variety of liquid droplet ejecting apparatuses provided with a plurality of nozzle rows. The following describes the drive circuit of the recording head disclosed in the Patent Document 1, wherein ink particles are ejected while a recording head containing a row of nozzles for four colors (Y, M, C and K) is moved for scanning in the main scanning direction of the carriage.
The head driver is made of ICs. One head driver is arranged for each of the four colors (Y, M, C and K). Each driver head contains a shift register, a latch, a digital comparator, a selection gate, a level shifter, a driver and a counter. Each head driver is connected to a 128-bit×3 shift register, and the image data from the line memory is stored in this shift register on a temporary basis.
The shift register has a storage capacity for storing the image data having the number of pixels equivalent to one-time ejection from the nozzle head, and is used to memorize the 128-pixel image data arranged in the sub-scanning direction. When the carriage has reached the position suited for recording, the control circuit outputs a LOAD signal. Upon receipt of the LOAD signal, the latch latches the image data outputted in parallel from the shift register.
The yellow (Y) image data is sent to the head driver from the line memory using a 3-bit data signal line. The yellow 128-pixel image data having been sent to the head driver is subjected to parallel processing, and recording is implemented by the head Y.
Similarly, the magenta (M) image data is sent from the line memory to the head driver, and recording is implemented by the head M. The cyan (C) image data is sent from the line memory to the head driver, and recording is implemented by the head C. The black (K) image data is sent from the line memory to the head driver, and recording is implemented by the head K.
The carriage starts one reciprocating motion based on the information obtained by encoder detection. When it has reached a predetermined position during its travel in the outward direction, the AND gate allows the TRGIN signal for starting ink ejection to be sent to the head driver through the control circuit. Upon receipt of the aforementioned TRGIN signal, the head driver sends the drive signal and ink is ejected from the head.
[Patent Document 1] Japanese Non-examined Patent Application Publication H10-250064
In recent years, there has been a drastic increase in the amount of data to be processed, due to the increasing number of gradations in recording data, higher density in the recording head and an increasing number of nozzles. This has consumed a lot of time for data transmission.
In the drive circuit corresponding to one nozzle row as in the conventional drive circuit, the position of ink arrival is adjusted at a pitch finer than the pixel pitch for each nozzle row, if there is only one latch. Accordingly, when different timing is used for ejection from each nozzle row, timing for data transmission to the shift register must be changed for each nozzle row.
This requires that the trigger for sending the data to the shift register corresponding to each nozzle row should be produced for each nozzle, with the result that complicated trigger control has to be provided. Especially when there are Y, M, C and K nozzle rows are provided, and a plurality of nozzle rows are provided for each color, the structure will become more complicated.
The timing for transmitting data to the shift register is the same for each row. This makes it essential to increase the data transmission speed or decrease the recording speed more than necessary.
The object of the present invention is to solve the aforementioned problems and to provide a liquid droplet ejecting apparatus and liquid droplet ejecting method capable of effective trigger processing for data transmission to the shift register, without having to overly increase the data transmission speed or decrease the recording speed, and further capable of adjusting the position for arrival of liquid droplets for each nozzle row at a pitch finer than the pixel pitch.